"Terra Preta de Indio" (Amazonian Dark Earths; earlier also called "Terra Preta do Indio" or Indian Black Earth) is the local name for certain dark earths in the Brazilian Amazon region. These dark earths occur, however, in several countries in South America and probably beyond. They were most likely created by pre-Columbian Indians from 500 to 2500 years B.P. and abandoned after the invasion of Europeans (Smith, 1980; Woods et al., 2000). However, many questions are still unanswered with respect to their origin, distribution, and properties.

Inspired by the fascinating properties of Terra Preta de Indio, bio-char is a soil amendment that has the potential to revolutionize concepts of soil management. While "discovered" may not be the right word, as bio-char (also called charcoal or biomass-derived black carbon) has been used in traditional agricultural practices as well as in modern horticulture, never before has evidence been accumulating that demonstrates so convincingly that bio-char has very specific and unique properties that make it stand out among the opportunities for sustainable soil management.

Most often, biofuels are seen as being 'carbon- neutral' in that they do not add CO2 to the atmosphere. When they are burned for energy, CO2 is emitted, but it gets taken up again as the new biomass grows, thus closing the carbon cycle and resulting in a neutral balance. This is the commonly held view of how biofuels are 'green'. In an early text, however, we hinted at the possibility of bioenergy doi

ABSTRACT
Black carbon (BC) is a major fraction (up to 35%, depending on methods used) of
soil organic carbon (SOC) in some of the most fertile and extensively cropped soils
of the world (Mollisols, Andisols, Terra Preta de Indio). Although BC is produced via
biomass burning in many ecosystems, it accumulates as a component of SOC in only
a few. Soils enriched in BC are not necessarily found in areas with the highest fire frequencies (savannah) or with the largest black carbon production (woody vegetation).

Above ground, rainforests like the Amazon basin flourish as biological hot spots with exuberant growth and a riot of plant and animal species.

But the red and yellow soils below are notoriously poor in nutrients and organic matter. Once the lush vegetation is cleared, the heavy rains and tropical sun quickly decompose even that small reservoir.

Except not in thousands of patches dotted along the Amazon River and its tributaries, where dark, friable soil extends metres deep, fertile in nutrients and organic material. In total, an area the size of France may be covered by this Indian black earth, called terra preta do Indio in Portuguese.

"The textbooks say it shouldn't be there. That's justification enough for me to explore why it is there," says Johannes Lehmann, a Cornell University professor specializing in the chemistry and geology of soils.

Many soils of the lowland humid tropics are thought to be too infertile to support sustainable agriculture. However, there is strong evidence that permanent or semi-permanent agriculture can itself create sustainably fertile soils known as 'Terra Preta' soils. These soils not only contain higher concentrations of nutrients such as nitrogen, phosphorus, potassium and calcium, but also greater amounts of stable soil organic matter. Frequent findings of charcoal and highly aromatic humic substances suggest that residues of incomplete combustion of organic material (black carbon) are a key factor in the persistence of soil organic matter in these soils. Our investigations showed that 'Terra Preta' soils contained up to 70 times more black carbon than the surrounding soils. Due to its polycyclic aromatic structure, black carbon is chemically and microbially stable and persists in the environment over centuries. Oxidation during this time produces carboxylic groups on the edges of the aromatic backbone, which increases its nutrient-holding capacity. We conclude that black carbon can act as a significant carbon sink and is a key factor for sustainable and fertile soils, especially in the humid tropics.

This book publication emerged from a meeting in Benicassim, Spain, in 2001. A group of enthusiastic scientists from diverse backgrounds decided that it is time to present a comprehensive overview over research on the so-called "Terra Preta de Indio", or Amazonian Dark Earths. Authors were invited to cover a wide variety of aspects around these fascinating soils, and met what became the first International Workshop on Terra Preta de Indio, in Manaus in July 2002. The frequent interactions and the workshop meeting ensured that this publication became a major text book on Amazonian Dark Earths. It is published by Kluwer Academic Publishers in The Netherlands

Terra Preta (do indio) is a black earth-like anthropogenic soil with enhanced fertility due to high levels of soil organic matter (SOM) and nutrients such as nitrogen, phosphorus, potassium, and calcium embedded in a landscape of infertile soils (see soil profiles below). Terra Preta soils occur in small patches averaging 20 ha, but 350 ha sites have also been reported. These partly over 2000 years old man made soils occur in the Brazilian Amazon basin and other regions of South America such as Ecuador and Peru but also in Western Africa (Benin, Liberia) and in the savannas of South Africa. Terra Preta soils are very popularby the local farmers and are used especially to produce cash crops such as papaya and mango, which grow about three times as rapid as on surrounding infertile soils.